The invention relates to devices for translational braking of a projectile on its trajectory.
Such devices are known, particularly in the field of artillery. EP138942 describes an artillery projectile which comprises a device for braking a warhead whose deployment is controlled on the trajectory.
Such a device makes it possible to improve the accuracy of artillery firing, taking into account the scatter due to variations in the initial velocity of the projectile. It is thus possible to aim the weapon so as to fire further than the target in sight; a fire control measures the true velocity of the projectile at the muzzle of the weapon barrel and a braking order is then transmitted to the projectile in order to reduce its range and bring it to the desired impact point.
The braking device described by this patent comprises either radially mobile ratchets or a flat frontal surface. Compared to the projectile cross section, the surface of these braking means is too small to give them sufficient braking capacity.
Patent WO98/01719 describes another braking device for projectiles. The device comprises four air brake plates stacked on each other and mobile radially with respect to the projectile. The braking surface is thus greatly increased (it constitutes approximately double the projectile cross section) with a reduced bulk inside the projectile body. This device, however, entails drawbacks.
The shapes of the plates are complicated when it comes to machining them; they also involve numerous notches that reduce their mechanical strength, especially when they are in their totally deployed position, which is the position where the stresses are at a maximum. Moreover, each plate is guided by the cooperation of pins integral with the ends of arms on the plate and which cooperate in the notches of a neighboring plate as well as a base plate. The arms have some flexibility, which impairs the reliability of the guidance function. This entails the risk of jamming and this risk is further increased by the fact that there is double guidance (on a neighboring plate and on a base plate). Finally, the plates are unlocked by means of two gas generators that move two retaining pins with each pin immobilizing two plates. Such a structure is liable to cause dissymmetries or jamming at the moment the plates are deployed; this, in turn, entails the risk of altering the projectile trajectory in a nonreproducible fashion.